Created
June 15, 2012 17:50
-
-
Save toji/2937842 to your computer and use it in GitHub Desktop.
Simple Javascript implementation of CMWC Psuedorandom algorithm
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
// This was basically ripped straight from http://en.wikipedia.org/wiki/Multiply-with-carry, just javscriptified. | |
var CMWCRand = function(seed) { | |
var i, PHI = 0x9e3779b9; | |
if(!seed) { seed = Date.now(); } | |
var Q = this.Q = new Uint32Array(4096); | |
this.c = 362436; | |
this.i = 4095; | |
Q[0] = seed; | |
Q[1] = seed + PHI; | |
Q[2] = seed + PHI + PHI; | |
for(i = 3; i < 4096; ++i) { | |
Q[i] = Q[i - 3] ^ Q[i - 2] ^ PHI ^ i; | |
} | |
}; | |
CMWCRand.prototype.randomUInt32 = function() { | |
var Q = this.Q; | |
var t, a = 18782; | |
var x, r = 0xfffffffe; | |
this.i = (this.i + 1) & 4095; | |
t = a * Q[this.i] + this.c; | |
this.c = (t >> 32); | |
x = t + this.c; | |
if (x < this.c) { | |
x++; | |
this.c++; | |
} | |
return (Q[this.i] = r - x); | |
}; | |
var randRange = 1.0/0xffffffff; | |
CMWCRand.prototype.random = function() { | |
return this.randomUInt32() * randRange; | |
}; |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment